New method of the directional modification of the electronic structure of single-walled carbon nanotubes by filling channels with metallic copper from a liquid phase

A method has been proposed and successfully implemented for filling the channels of single-walled carbon nanotubes with metallic copper by permeating with an aqueous solution of copper nitrate with subsequent thermal treatment. It has been demonstrated that the introduction of metallic copper into the channels of nanotubes leads to donor doping accompanied both by an increase in the Fermi energy of nanotubes and by the transfer of the electron density from introduced metal nanoparticles to the walls of nanotubes.     

Reconstruction of the signal produced by a directional sound source from remote multi-microphone recordings

A mathematical method for reconstructing the signal produced by a directional sound source from knowledge of the same signal in the far field, i.e., microphone recordings, is developed. The key idea is to compute inverse filters that compensate for the directional filtering of the signal by the sound source directivity, using a least-square error optimization strategy. Previous work pointed out how the method strongly depends on arrival times of signal in the microphone recordings. Two strategies are used in this paper for calculating the time shifts that are afterward taken as inputs, together with source directivity, for the reconstruction. The method has been tested in a laboratory environment, where ground truth was available, with a Polaroid transducer as source. The reconstructions are similar with both strategies. The performance of the method also depends on source orientation.     

Measurement of gas flow parameters by the laser produced breakdown method

A method of measuring gas flow parameters, based on testing the gas flow by shock waves, is described. The shock waves in the examined flow were produced by a pulsed laser beam focused on to the surface of an object. To illustrate the method, experimental data are presented dealing with gas parameters on the surface of a free-flying object.     

On the nature of the impulsive pressure produced by wire burst in water

It is shown that the impulsive pressure arising when a wire bursts in water is due to the products of a chemical reaction between the bursting wire and water. The dependence of the impulsive pressure amplitude on the bursting wire weight is satisfactory described by perfect gas laws.     

Spatial structures of spark channels in the breakdown phase

The cross sectional structure of spark discharges in the breakdown phase was investigated by means of anode evaporation patterns. Assuming the channel structure being determined by space charge effects reasonable agreement between computed initial channel diameters and experimental results was found.     

Nonstationary interaction of a supersonic flying object with extended low-density regions in the atmosphere

A three-dimensional numerical model is developed and the aerodynamic loads are determined for the three-dimensional flow acting on a blunt cone flying in the atmosphere along the boundary of a rarefied region, as functions of the degree of immersion of the surface of the body in low-density air. The nonstationary gas-and aerodynamic processes accompanying the entry and exit of the body from the rarefied region are studied. The aerodynamic coefficients obtained with an approximate model are compared with the three-dimensional calculations and found to be in satisfactory agreement with them. Zh. Tekh. Fiz. 68, 32–37 (November 1998)     

Statistics of breakdown centers during the propagation of laser radiation through a turbulent atmosphere

The statistics are examined for breakdown centers that arise in a polydisperse background aerosol during the propagation of intense laser radiation through a turbulent atmosphere.Translated from Izvestiya Vysshikh Uchebnikh Zavedenii, Fizika, No. 2, pp. 75–79, February, 1987.     

High-speed recording of laser- produced breakdown in air

A series of laser-produced breakdown interferograms has been obtained using five diffraction interferometers with pulsed ruby lasers serving as light sources. The interferograms and the results of their processing are presented in this article.     

Determination of copper content in soils and ores by laser-induced breakdown spectrometry

Features of electromagnetically induced transparency (EIT) in potassium vapors at the D₁ line of the ³⁹K isotope are studied. EIT resonances with a subnatural width of 3.5 MHz have been recorded upon excitation by two independent narrow-band diode lasers in a 1-cm-long cell filled with a natural mixture of potassium isotopes and buffer gas. The splitting of EIT resonances in potassium vapors in longitudinal and transverse magnetic fields has been studied for the first time. The splitted components also have a subnatural width. The smallness of the coupling factor of the hyperfine structure in ³⁹K atoms leads to a transition to the Paschen—Back regime at relatively weaker magnetic fields than in the case of Cs, Rb, and Na atoms. Practical applications of the phenomena under study are noted. The theoretical model well explains the experiment.     

Regimes of laser plasma expansion at optical breakdown in the normal atmosphere

Propagation regimes of a plasma (fast ionization wave, laser-supported radiation wave, and laser-supported detonation wave) generated by laser radiation in a wide range of intensities (5 × 10⁸?10¹¹ W/cm² ) are described. The regimes were analyzed on the basis of the calculated dependence of the propagation velocity on the laser radiation intensity. The lower bound of the velocity was used for the fast ionization wave. Calculation results agree with experimental data and show that the plasma propagates as a fast ionization wave in the above range of intensities.     

Inversion in an extended three-level medium produced by adiabatic population transfer

Features of the adiabatic population transfer are studied with the spatial evolution of interacting pulses propagating in an optically dense medium of three-level Λ-atoms taken into account. A self-consistent analytical solution describing the spatial-temporal dynamics of interacting short pulses under the conditions of adiabatic population transfer is constructed in the adiabatic approximation with consideration for the first nonadiabatic correction. Practically complete inversion on a forbidden transition determined by coherent (adiabatic) population transfer is shown to take place over a length of the medium, which may exceed the absorption length of a weak probing pulse in the absence of control radiation on the adjacent transition by several orders of magnitude.